1. Field of the Invention
The present invention relates generally to pipe wiping methods and apparatus and, more particularly, but not by way of limitation, to improved methods and apparatus for removing drilling mud and the like from drill pipe as it is removed from a wellbore by a drilling rig.
2. Description of the Prior Art
In the drilling of wells penetrating subterranean producing formations, various drilling fluids are utilized to maintain hydrostatic head on the formation being drilled, to lubricate the drill bit and to carry cuttings from the drill bit to the surface. Such drilling fluids are commonly referred to as drilling muds.
The drill bit is connected by a string of threadedly connected together drill pipe sections to a drilling rig at the surface. The drilling rig rotates the string of drill pipe and drill bit and additional drill pipe sections are continuously added to the drill string as the drilling progresses. When it is necessary to withdraw the string of drill pipe and drill bit from the wellbore, such as for the purpose of replacing a worn-out drill bit, the drill string is pulled out of the wellbore one drill pipe section at a time and the sections are disconnected. As the drill pipe sections are pulled out of the wellbore, the outside surfaces of the sections are covered with drilling fluid which makes their handling difficult, causes the floor of the drilling rig to be covered with drilling fluid which is slippery and hazardous to drilling rig personnel, brings about the waste of the drilling fluid and causes pollution of the atmosphere in that drilling fluids usually always contain some atmosphere polluting components.
Methods and apparatus for removing drilling fluid, oil and other substances from the outer surfaces of drill pipe have been developed and utilized heretofore. For example, in my co-pending U.S. patent application Ser. No. 334,968 filed Jan. 20, 1982, a pipe wiper apparatus is disclosed for installation over a wellbore which wipes drilling fluid from the surfaces of drill pipe as the drill pipe is pulled out of the wellbore. That apparatus includes a resilient annular ring formed of a size such that the central opening in the ring fits tightly against the outside surfaces of drill pipe. As the drill pipe is pulled through the ring it wipes drilling mud and other substances from the pipe. While such apparatus has been utilized successfully in drilling rig operations, the resilient annular wiping ring of the apparatus must be replaced on a relatively frequent basis since its wiping surfaces are continuously worn away as drill pipe is pulled through the apparatus.
By the present invention an improved pipe wiping method and apparatus are provided which bring about the more efficient wiping and removal of drilling fluid and the like from the outside surfaces of drill pipe, require much less frequent replacement of the resilient wiping member and provide a positive seal between the apparatus and the drill pipe which can facilitate the prevention of blowouts, etc.